The phenomenon of compulsive hoarding, characterized by the acquisition of and failure to discard a large number of items, is increasingly recognized as a significant public health burden. Hoarding is most frequently associated with obsessive compulsive disorder (OCD), which is one of the top ten leading causes of disability world wide. Emerging research has found that compared to other forms of OCD, hoarding is linked with greater severity, increased disability across domains of functioning, health risks to the individual and their community, and poorer treatment response. Despite the magnitude of the impairment associated with hoarding, empirical research is still in the nascent stages and many facets of the phenomenology, including an understanding of the underlying vulnerability and risk factors, are yet unknown. The overall aim of the current proposal is to increase our knowledge of the etiology and maintenance of hoarding. A central tenet of a recent cognitive behavioral model of hoarding states that the core features of the behavior are in fact forms of avoidance. Surprisingly, few empirical investigations to date have attempted to elucidate the basis for this facet of hoarding. Research within the broader field of anxiety disorders points to a number of factors that play a role in explaining avoidance in anxiety, and which may also be applicable to hoarding. The proposed program of research will investigate two forms of affective-style (i.e., anxiety sensitivity and distress tolerance) that may operate as risk factors for the avoidance component of hoarding. In addition, we will assess the role of stress as a catalyst for the exacerbation of hoarding behavior, along with the moderating effects stress may have on the affective-style risk factors being considered. The first study will employ a multimethod approach to definitively assess anxiety sensitivity and distress tolerance in a non-treatment seeking sample of individuals with clinically significant hoarding, compared to a non-clinical control group. Importantly, we will use both self-report and behavioral measures to tap avoidance hoarding behavior. The second study will be an experimental investigation that will randomize an analogue, premorbid sample into a challenge or non-challenge condition. This particular study will similarly utilize a behavioral measure of hoarding behavior and will assess the influence of stress as a further risk factor for amplified hoarding symptoms. The interaction between stress and affective-style, with regard to avoidance hoarding behavior, will also be examined. Together, the two studies proposed in this program of research will provide critical knowledge regarding vulnerabilities for hoarding and will lay important groundwork for future treatment and etiological investigations. [unreadable] [unreadable] [unreadable]